package com.meego.common.html.select;

import com.meego.common.html.helper.Validate;
import com.meego.common.html.nodes.Element;
import java.util.Collection;
import java.util.LinkedHashSet;

/**
 * CSS-like element selector, that finds elements matching a query.
 * <p/>
 * <h2>Selector syntax</h2> A selector is a chain of simple selectors, separated by combinators. Selectors are case
 * insensitive (including against elements, attributes, and attribute values).
 * <p/>
 * The universal selector (*) is implicit when no element selector is supplied (i.e. {@code *.header} and
 * {@code .header} is equivalent).
 * <p/>
 * <table> <tr><th>Pattern</th><th>Matches</th><th>Example</th></tr> <tr><td><code>*</code></td><td>any
 * element</td><td><code>*</code></td></tr> <tr><td><code>tag</code></td><td>elements with the given tag
 * name</td><td><code>div</code></td></tr> <tr><td><code>ns|E</code></td><td>elements of type E in the namespace
 * <i>ns</i></td><td><code>fb|name</code> finds
 * <code>&lt;fb:name></code> elements</td></tr> <tr><td><code>#id</code></td><td>elements with attribute ID of
 * "id"</td><td><code>div#wrap</code>,
 * <code>#logo</code></td></tr> <tr><td><code>.class</code></td><td>elements with a class name of
 * "class"</td><td><code>div.left</code>,
 * <code>.result</code></td></tr> <tr><td><code>[attr]</code></td><td>elements with an attribute named "attr" (with any
 * value)</td><td><code>a[href]</code>,
 * <code>[title]</code></td></tr> <tr><td><code>[^attrPrefix]</code></td><td>elements with an attribute name starting
 * with "attrPrefix". Use to find elements with HTML5 datasets</td><td><code>[^data-]</code>,
 * <code>div[^data-]</code></td></tr> <tr><td><code>[attr=val]</code></td><td>elements with an attribute named "attr",
 * and value equal to "val"</td><td><code>img[width=500]</code>,
 * <code>a[rel=nofollow]</code></td></tr> <tr><td><code>[attr^=valPrefix]</code></td><td>elements with an attribute
 * named "attr", and value starting with "valPrefix"</td><td><code>a[href^=http:]</code></code></td></tr>
 * <tr><td><code>[attr$=valSuffix]</code></td><td>elements with an attribute named "attr", and value ending with
 * "valSuffix"</td><td><code>img[src$=.png]</code></td></tr> <tr><td><code>[attr*=valContaining]</code></td><td>elements
 * with an attribute named "attr", and value containing "valContaining"</td><td><code>a[href*=/search/]</code></td></tr>
 * <tr><td><code>[attr~=<em>regex</em>]</code></td><td>elements with an attribute named "attr", and value matching the
 * regular expression</td><td><code>img[src~=(?i)\\.(png|jpe?g)]</code></td></tr> <tr><td></td><td>The above may be
 * combined in any order</td><td><code>div.header[title]</code></td></tr> <tr><td><td
 * colspan="3"><h3>Combinators</h3></td></tr> <tr><td><code>E F</code></td><td>an F element descended from an E
 * element</td><td><code>div a</code>,
 * <code>.logo h1</code></td></tr> <tr><td><code>E > F</code></td><td>an F direct child of
 * E</td><td><code>ol > li</code></td></tr> <tr><td><code>E + F</code></td><td>an F element immediately preceded by
 * sibling E</td><td><code>li + li</code>,
 * <code>div.head + div</code></td></tr> <tr><td><code>E ~ F</code></td><td>an F element preceded by sibling
 * E</td><td><code>h1 ~ p</code></td></tr> <tr><td><code>E, F, G</code></td><td>all matching elements E, F, or
 * G</td><td><code>a[href], div, h3</code></td></tr> <tr><td><td colspan="3"><h3>Pseudo selectors</h3></td></tr>
 * <tr><td><code>:lt(<em>n</em>)</code></td><td>elements whose sibling index is less than
 * <em>n</em></td><td><code>td:lt(3)</code> finds the first 2 cells of each row</td></tr>
 * <tr><td><code>:gt(<em>n</em>)</code></td><td>elements whose sibling index is greater than
 * <em>n</em></td><td><code>td:gt(1)</code> finds cells after skipping the first two</td></tr>
 * <tr><td><code>:eq(<em>n</em>)</code></td><td>elements whose sibling index is equal to
 * <em>n</em></td><td><code>td:eq(0)</code> finds the first cell of each row</td></tr>
 * <tr><td><code>:has(<em>selector</em>)</code></td><td>elements that contains at least one element matching the
 * <em>selector</em></td><td><code>div:has(p)</code> finds divs that contain p elements </td></tr>
 * <tr><td><code>:not(<em>selector</em>)</code></td><td>elements that do not match the <em>selector</em>. See also
 * {@link Elements#not(String)}</td><td><code>div:not(.logo)</code> finds all divs that do not have the "logo" class.<br
 * /><code>div:not(:has(div))</code> finds divs that do not contain divs.</code></td></tr>
 * <tr><td><code>:contains(<em>text</em>)</code></td><td>elements that contains the specified text. The search is case
 * insensitive. The text may appear in the found element, or any of its
 * descendants.</td><td><code>p:contains(jsoup)</code> finds p elements containing the text "jsoup".</td></tr>
 * <tr><td><code>:matches(<em>regex</em>)</code></td><td>elements whose text matches the specified regular expression.
 * The text may appear in the found element, or any of its descendants.</td><td><code>td:matches(\\d+)</code> finds
 * table cells containing digits.
 * <code>div:matches((?i)login)</code> finds divs containing the text, case insensitively.</td></tr>
 * <tr><td><code>:containsOwn(<em>text</em>)</code></td><td>elements that directly contains the specified text. The
 * search is case insensitive. The text must appear in the found element, not any of its
 * descendants.</td><td><code>p:containsOwn(jsoup)</code> finds p elements with own text "jsoup".</td></tr>
 * <tr><td><code>:matchesOwn(<em>regex</em>)</code></td><td>elements whose own text matches the specified regular
 * expression. The text must appear in the found element, not any of its
 * descendants.</td><td><code>td:matchesOwn(\\d+)</code> finds table cells directly containing digits.
 * <code>div:matchesOwn((?i)login)</code> finds divs containing the text, case insensitively.</td></tr>
 * <tr><td></td><td>The above may be combined in any order and with other
 * selectors</td><td><code>.light:contains(name):eq(0)</code></td></tr> </table>
 *
 * @see Element#select(String)
 */
public class Selector {

    private final Evaluator evaluator;
    private final Element root;

    private Selector(String query, Element root) {
        Validate.notNull(query);
        query = query.trim();
        Validate.notEmpty(query);
        Validate.notNull(root);

        this.evaluator = QueryParser.parse(query);

        this.root = root;
    }

    /**
     * Find elements matching selector.
     *
     * @param query CSS selector
     * @param root root element to descend into
     * @return matching elements, empty if not
     */
    public static Elements select(String query, Element root) {
        return new Selector(query, root).select();
    }

    /**
     * Find elements matching selector.
     *
     * @param query CSS selector
     * @param roots root elements to descend into
     * @return matching elements, empty if not
     */
    public static Elements select(String query, Iterable<Element> roots) {
        Validate.notEmpty(query);
        Validate.notNull(roots);
        LinkedHashSet<Element> elements = new LinkedHashSet<Element>();

        for (Element root : roots) {
            elements.addAll(select(query, root));
        }
        return new Elements(elements);
    }

    private Elements select() {
        return Collector.collect(evaluator, root);
    }

    // exclude set. package open so that Elements can implement .not() selector.
    static Elements filterOut(Collection<Element> elements, Collection<Element> outs) {
        Elements output = new Elements();
        for (Element el : elements) {
            boolean found = false;
            for (Element out : outs) {
                if (el.equals(out)) {
                    found = true;
                    break;
                }
            }
            if (!found) {
                output.add(el);
            }
        }
        return output;
    }

    public static class SelectorParseException extends IllegalStateException {

        private static final long serialVersionUID = -7572052759399834840L;

        public SelectorParseException(String msg, Object... params) {
            super(String.format(msg, params));
        }
    }
}
